1. Technical Field of the Invention
This invention relates to telecommunication systems. More particularly, and not by way of limitation, the present invention is directed to a system and method of providing access to Intelligent Network (IN) services from a plurality of dissimilar telecommunications networks.
2. Description of Related Art
Telecommunications networks may be broadly categorized as wireline or wireless. In both types of networks, subscribers are often provided with enhanced subscriber services by accessing an Intelligent Network (IN). In general, a Service Switching Point (SSP) in the IN is utilized to access an IN Service Control Point (IN-SCP) which executes service scripts in order to provide the IN services. The data for the IN services may be stored within the SCP or in a separate IN Service Data Point (IN-SDP).
Within the wireless category of telecommunications networks, two main mobile telecommunications technologies are utilized: Global System for Mobile Communications (GSM) and the ANSI-41 standard. ANSI-41 networks may utilize either Time Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA) technology for digital sharing of network bandwidth. Both GSM and ANSI-41 networks provide IN services to their subscribers, but the services are accessed in different ways. In general, ANSI-41 has standards for triggering access to a separate IN network, while GSM has built-in IN services. A subscriber with an ANSI-41-compliant mobile station (MS) may access the IN services only in an ANSI-41 network, while a subscriber with a GSM-compliant MS may access the IN services only in a GSM network. As long as a subscriber remains within the appropriate network for his type of MS, there is no problem. However, when the subscriber crosses from a network based on one technology to a network based on the other technology, there is no linkage to enable the subscriber to access IN services.
A GSM overlay network is implemented by system operators who are transitioning from ANSI-41 to GSM. The GSM overlay network may cover approximately the same geographic area as the underlying ANSI-41 network. The overlay network enables the operator to provide GSM services to those mobile subscribers who have GSM-compliant MSs. For those subscribers who have ANSI-41-compliant MSs, the operator can continue to provide ANSI-41 services. Eventually, as the original ANSI-41 MSs are replaced with GSM MSs, the system operators may eliminate the ANSI-41 network and discontinue ANSI-41 services.
A problem with overlay networks, however, is the high cost to the operators of duplicating all of the services that are provided in each network. In the case of IN services, these services must currently be duplicated since the GSM and ANSI-41 networks utilize different and incompatible methods of accessing the IN services. It would be desirable to provide the ANSI-41 subscribers with direct access to some or all of the GSM IN services, thereby eliminating the cost of duplicating these services. For example, the GSM network provides a Prepaid service that allows a mobile subscriber to prepay for an amount of telephone time. An account balance is maintained for the subscriber in an IN-SDP, and whenever the subscriber uses his MS to place or receive a call, the corresponding cost of the call is deducted from the subscriber's prepaid account. The service is convenient for the subscriber, and can be activated using the subscriber's existing telephone number.
ANSI-41 networks also have a Prepaid service, but it is not as convenient for the subscriber. The ANSI-41 service is a trunking-based solution that requires that the subscriber obtain a different telephone number for use with the Prepaid service. It would be advantageous for ANSI-41 subscribers to be able to access the GSM Prepaid service in the GSM overlay network, thus eliminating the requirement to have a different telephone number for the Prepaid account. The operator would also save the cost of implementing and maintaining two different types of Prepaid services. However, ANSI-41 subscribers cannot currently access and utilize the GSM Prepaid service.